Mechanistically distinct mouse models for CRX-associated retinopathy

Area of Science:

• Genetics
• Molecular Biology
• Ophthalmology

Background:

• Cone-rod homeobox (CRX) is crucial for photoreceptor gene regulation.
• Mutations in CRX cause inherited retinal diseases like Retinitis Pigmentosa (RP), Cone-Rod Dystrophy (CoRD), and Leber Congenital Amaurosis (LCA).
• Existing heterozygous Crx Knock-Out (KO) mice do not accurately model dominant human CRX diseases.

Purpose of the Study:

• To develop and characterize novel mouse models that accurately reflect the spectrum of CRX-associated retinopathies.
• To investigate the distinct molecular mechanisms underlying different CRX mutations and their associated disease severities.
• To provide platforms for testing therapeutic strategies for CRX-related inherited retinal diseases.

Main Methods:

• Generation of two Crx Knock-IN (K-IN) mouse models: Crx(E168d2) and Crx(R90W).
• Phenotypic analysis including retinal function, photoreceptor morphology, and gene expression in mutant mice.
• In vitro studies to assess the transcriptional activity and dominant-negative effects of mutant CRX proteins.

Main Results:

• Heterozygous E168d2 mice exhibit severe retinal dysfunction and degeneration, mirroring human CoRD/LCA, while R90W mice show milder phenotypes.
• Homozygous mutations in both models lead to blindness and rapid photoreceptor loss.
• The E168d2 mutation demonstrates a higher level of mutant CRX expression and a stronger antimorphic effect, interfering more with wild-type CRX function.
• Reduced mutant allele expression in E168d2neo/+ mice significantly ameliorates the retinal phenotype, highlighting the importance of expression levels.

Conclusions:

• The E168d2 and R90W mouse models represent distinct mechanistic pathways for CRX-associated retinopathies.
• These models are valuable tools for elucidating disease mechanisms and evaluating novel therapeutic interventions for inherited retinal diseases caused by CRX mutations.